Pig eyes cure blindness

By Zhang Yiqian Source:Global Times Published: 2015-6-10 19:28:01

Bioengineered corneas to enter mass production in China

In July, an artificial cornea that Chinese scientists spent more than 10 years developing will go into mass production. The corneas come from the eyes of pigs. Doctors say this will help close the gap between number of blind patients and donors.

Medical workers implant a cornea into a patient's eye in a hospital in Wuhan, Central China's Hubei Province. Photo: IC

Huang Yuanzhen has had a pig's cornea in her right eye for five years.

She's able to joke about it now, telling this fact to people she meets to surprise them. But when she first heard that doctors wanted to implant a slice of pig eye into her body, she was frightened and disgusted.

In 2010, the then 52-year-old farmer living in Songzi township, Central China's Hubei Province, accidentally poked her right eye with a bamboo splint while working in the field. She immediately felt pain and couldn't open her eye.

When she could, finally, she could see nothing but darkness. In the next few months, she went from hospital to hospital to seek help, accompanied by her family. She was told by doctors that she had an ulcer that covered more than half of her cornea, and was diagnosed as blind in that eye.

But the turning point came soon, when her doctor at Wuhan Union Hospital, Zhang Mingchang, asked whether she'd be open to transplanting an artificial cornea into her eye. She was also told a pig cornea was the main material for this new invention.

"I felt scared about it being a pig's eye," Huang said. "But the doctor said if I choose this, the company [that developed the cornea] would pay for the surgery." Besides, she constantly fell or bumped into people with only one eye, and her right eye throbbed with pain.

She decided to accept the surgery.

Vision for a cure

About 10 years before Huang accepted her surgery, Jin Yan, a professor and researcher at The Fourth Military Medical University, received a request from Hong Kong-based company China Regenerative Medicine International (CRMI).

The company asked him if he would like to cooperate with them to develop artificial corneas.

In China, keratitis, or inflammation of the cornea, is the second biggest cause of blindness, after cataracts. According to World Health Organization data, there are more than 4 million patients with keratitis in China, and the number is increasing by 100,000 each year.

The surgical solution for the disease is a cornea transplant. But there is a large gap between the number of patients and cornea donations.

"There are about 5,000 donations every year, it covers only a very small number of patients," Jin said.

Many teams around the world have tried developing artificial corneas. But so far none succeeded beyond clinical tests.

"Doctors and researchers have long been trying to develop artificial corneas," he said. "But due to its complex structure and fragility nobody has succeeded before."

Jin had previously worked with CRMI in developing a prosthetic skin, which speeds up patients' healing process and is an effective treatment for ulcers. So when he started trying to develop artificial corneas, he thought of using collagen.

But soon his team ran into the same dilemma as international researchers. They found out that there's no way collagen can imitate the thin but complicated fiber structures in a human cornea. That's when the team turned to animals.

The animal's eye needed to be similar to a human's. The animal need to be easy to raise and keep healthy. Based on these needs, the team considered cats and goats, and finally settled on pigs.

Choosing an animal was just the first step. The more difficult part was to figure out how to counter rejection by the host body after transplantation.

The most common way is to remove donor cells and antigen molecules to diminish the host immune reaction, but it was hard to find a method that could both remove the cells and leave the pig cornea's structure intact.

Developing this procedure took a few years.

After that, Jin's team conducted thousands of animal experiments. More than 10,000 pigs were used by the research team.

The team later named the artificial cornea "Aixintong," a generic sounding name that offers no clue to the product's porcine pedigree.

Patients' gospel

Huang tried opening up her eyes after the surgery and found her vision to be fuzzy.

She was not aware that she had become the first person in China to receive an artificial cornea transplant.

Her vision gradually improved and her right eye recovered to about 80 percent the level of her left eye.

She was not aware that after her, doctors were encouraged, and another 114 transplants were performed in five hospitals across China. Out of these transplants, 109 succeeded.

These patients were required to come back for re-examinations in a few months. The result was surprisingly good: the artificial corneas worked about as well as natural ones.

In April, the China Food and Drug Administration gave Aixintong a medical certificate, recognizing the product as the first cornea bioengineered and patented by Chinese scientists and granting it approval to be used.

In July, the artificial cornea will be mass-produced and used in surgery.

Right now, some patients are already inquiring about the cornea in the Wuhan Union Hospital, where Huang Yuanzhen got treated. In the past, people who couldn't wait on a donated cornea often had to have their eyeball removed because it could become infected.

In January 2015, Huang Jiefu, director of the human organ transplant clinical technology application management committee under the National Health and Family Planning Commission, announced that China's human organs will be sourced only from donors, not from executed criminals.

Facing a situation with even fewer organs to be used in transplantation, the Chinese scientists pushed to mass-produce Aixintong.

Preparations to use the artificial corneas are in place. According to media reports, the Shandong Ophthalmology Hospital has begun training surgeons to implant the artificial cornea. The program is hoping to recruit 100 doctors this year.

A doctor in Shandong Province told the China Youth Daily that in the future, patients may be able to get cornea transplants within two days of diagnosis.

In order to supply pig corneas, scientists established a pig farm in Shenzhen, Guangdong Province. All pigs in the farm have their own "ID number."

If a cornea is found to be faulty after transplant, scientists can easily track which pig it came from.

Doubts remain

Jin said many questioned his research at the beginning. When he went to academic conferences, only a small number of people thought he might succeed.

Despite his success, his innovation has not been widely adopted internationally at this time.

After Jin's team published the results, a research team in the US published a paper in the scientific journal of the Association of Research in Vision and Ophthalmology, pointing out there may be imperfections in the decellularization methods currently used by international research teams. It names Jin's team in particular.

Even doctors in China had doubts when they were conducting clinical experiments with Aixintong. The invention was too new.

Zhang Mingchang from Wuhan Union Hospital said when he was performing surgery for Huang, he had his doubts. He didn't even know whether Aixintong was safe, let alone whether it would work.

When performing surgery, he had a few backup corneas, including one from a human donor, in case Aixintong failed.

But after Huang's recovery and after the re-evaluation of her eye's condition in 2013, Zhang's doubts gradually vanished.

He became even more optimistic about the prospect of Aixintong after completing 47 transplantations as a clinical trial and maintaining a success rate of over 90 percent.

Huang had no idea of the doubts and controversies involving Aixintong.

In May, she was invited by the CRMI to come to the launching ceremony of Aixintong in Beijing. Afterwards, she went to Tiananmen Square for the first time. It was unbelievable that she could see those sites with both eyes, especially when she thinks back about the days she thought she would be blind in one eye forever.

During the ceremony, she couldn't explain how the cornea worked, but she kept saying, "This works well, I can do work on the farm fields again."